Field of the Invention
The present invention concerns a method and a magnetic resonance system for functional MR imaging with which in particular brain activities can be graphically depicted.
Description of the Prior Art
A non-invasive examination of brain activities is possible with functional nuclear magnetic resonance tomography (fMRI). Comparison measurements with regard to the brain of the patient in a steady state, and the brain after being exposed to stimuli, show which brain regions are stimulated or affected, and how strongly, by the stimuli. The stimuli can be of pain stimuli, optical stimuli, acoustic stimuli or other stimulation, for example the placement of a block of ice on the skin.
According to the prior art, most often the BOLD (“Blood Oxygen Level Dependent”) signal is measured in fMRI examinations. The BOLD signal is dependent on the oxygen concentration within the blood. The susceptibility of blood changes depending on the oxygen content therein, which in turn can be detected by MR measurements. In other words: in fMRI, with suitable methods it is determined at which points of the brain the oxygen reaction changes with and without stimulus. The activity of individual brain regions is then directly identified from these results. According to the prior art, fast measurement methods that operate with an EPI sequence (“Echoplanar Imaging”) are used, for example.